Effects of nanobubble water on digestate soaking hydrolysis of rice straw.

This study investigated the performance of combined nanobubble water (NW) and digestate in the soaking hydrolysis process. Two types of NW (CO2NW and O2NW) with digestate were used to soak rice straw for 1, 2, 3, 5, and 7 days. During soaking process, the volatile fatty acids (VFA) concentration in the treatment with O2NW and digestate for 3 days (O2NW-3 d) reached 7179.5 mg-HAc/L. Moreover, the highest specific methane yield (SMY) obtained in this treatment could reach 336.7 NmL/gVS. Although the addition of NW did not significantly increase SMY from digestate soaking, NW could accelerate the rate of methane production and reduce digestion time of T80. The enrichment of Enterobacter in the soaking process was observed when using CO2NW and O2NW as soaking solutions which played important roles in VFA production. This study provides a new insight into environment-friendly enhanced crop straw pretreatment, combining NW and digestate soaking hydrolysis.

Synergistic effect of hydrothermal sludge and food waste in the anaerobic co-digestion process: microbial shift and dewaterability.

While thermal hydrolysis technology is commonly employed for sewage sludge treatment in extensive wastewater treatment facilities, persistent challenges remain, including issues such as ammonia-induced digestive inhibition and reduced productivity stemming from nutrient deficiency within the hydrothermal sludge. In this study, the effects of hydrothermal sludge-to-food waste mixing ratios and fermentation temperatures on anaerobic co-digestion were systematically investigated through a semi-continuous experiment lasting approximately 100 days. The results indicated that anaerobic co-digestion of hydrothermal sludge and food waste proceeded synergistically at any mixing ratio, and the synergistic effect is mainly attributed to the improvement of carbohydrate removal and digestive system stability. However, thermophilic digestion did not improve the anaerobic performance and methane yield. On the contrary, mesophilic digestion performed better in terms of organic matter removal, especially in the utilization of soluble carbohydrates, soluble proteins, and VFAs. Microbial community analysis revealed that the transition from mesophilic to thermophilic anaerobic co-digestion prompts changes in the methane-producing pathways. Specifically, the transition entails a gradual shift from pathways involving acetoclastic and hydrogenotrophic methanogenesis to a singular hydrogenotrophic methanogenesis pathway. This shift is driven by thermodynamic tendencies, as reflected in Gibbs free energy, as well as environmental factors like ammonia nitrogen and volatile fatty acids. Lastly, it is worth noting that the introduction of food waste did lead to a reduction in cake solids following dewatering. Nevertheless, it was observed that thermophilic digestion had a positive impact on dewatering performance.

Optimal deployment of thermal hydrolysis and anaerobic digestion to maximize net energy output based on sewage sludge characteristics.

Thermal hydrolysis (TH) is widely employed in combination with anaerobic digestion (AD) to efficiently treat primary sludge and waste-activated sludge in municipal wastewater treatment plants. In this study, four different scenarios-conventional AD (S1), TH-AD (S2), AD-TH-AD (S3), and characteristics-based AD-TH-AD (S4, primary AD only for primary sludge)-were evaluated to determine the optimal deployment of TH and AD for treating primary sludge and waste-activated sludge to maximize net energy output. The maximum net energy output of 4899 MJ/t-TSfed (per ton total solids of sludge fed) was achieved in S4 when assuming the recovered heat was only used for AD heating and surplus heat was wasted, and the net energy output of S4 was 70.8 % higher than that of S1 and 48.6 % higher than that of S2. This remarkable improvement was attributed to a reduction of > 15.2 % in refractory compounds, resulting in a 17 % increase in methane yield. Importantly, this study provides the first comparison of refractory compounds between inter-thermal hydrolysis (inter-TH) and pre-thermal hydrolysis (pre-TH) using a simulated A2O process. Overall, this study provides innovative insights and strategies for enhancing the TH and AD process performance based on the specific characteristics of sewage sludge derived from wastewater treatment plants.

Two-step anaerobic digestion of rice straw with nanobubble water.

Lignocellulose usually requires pretreatment to improve biogas production. To enhance lignocellulose biodegradability and improve anaerobic digestion (AD) efficiency, different types (N2, CO2, and O2) of nanobubble water (NW) were applied in this study as soaking agent and AD accelerant to increase the biogas yield of rice straw. The results showed that the cumulative methane yields of treating with NW in two-step AD increased by 11.0%-21.4% compared with untreated straw. The maximum cumulative methane yield was 313.9±1.7 mL/gVS in straw treated with CO2-NW as soaking agent and AD accelerant (PCO2-MCO2). The application of CO2-NW and O2-NW as AD accelerants increased bacterial diversity and relative abundance of Methanosaeta. This study suggested that using NW could enhance soaking pretreatment and methane production of rice straw in two-step AD; however, combined treatment with inoculum and NW or microbubble water in the pretreatment needs to compare in future.

[The effect of isoflurane induced hypotension on intraoperative cerebral vasospasm in intracranial aneurysm surgery].

OBJECTIVE: To evaluate whether isoflurane induced hypotension increases the incidence of cerebral vasospasm in intracranial aneurysm surgery. METHODS: Thirty consecutive patients undergoing intracranial aneurysmal surgery without preexisting cerebral ischemia were prospectively randomized into 2 groups: isoflurane induced hypotension group (group A, n = 15) and isoflurane maintained anesthesia group (group B, n = 15). The patients in the group A were performed isoflurane induced hypotension after dura opening by increasing the inhaled concentration of isoflurane to decrease the mean arterial pressure (MAP) by 30 - 40 percent of that of baseline value. After the aneurysm was clipped, the concentration of inhaled isoflurane was decreased so as to stop blood pressure reduction. The patient in group B was given 1 minimum alveolar concentration (MAC) of isoflurane during the whole procedure. The indicators of blood circulation were measured before blood pressure reduction, 30 minutes after blood pressure reduction, just after the clipping of the aneurysm, and 30 minutes after stopping blood pressure reduction. The S100B protein level in cerebrospinal fluid was observed before the controlled hypotension and 0, 2, and 4 h after the aneurysm was clipped. Assessment of the mean blood flow velocity of parent artery and its main branches was performed by microvascular ultrasonics before and after the aneurysm was clipped. The patients were followed-up for one week after the operation to observe the neurological complication. RESULTS: The MAP was decreased from 95 mm Hg +/- 12 mm Hg to 59 mm Hg +/- 5 mm Hg 30 minutes after the induced hypotension, and resumed to 75 mm Hg +/- 8 mm Hg 30 minutes after the aneurysm was clipped. Compared with those in the group B, both the total systemic vascular resistance and myocardial contract acceleration were decreased in group A, whereas the cardiac output and heart rate remained stable. (2) 4 hours after the aneurysm was clipped the S100B protein level in CSF was increased significantly in both groups, and that in the group A being significantly higher than that in the group B (t = 2.854, P < 0.01). (3) In the group A, the mean arterial flow velocity of distal parent vessels increased by more than 30 percent in 8 out of the 15 patients and 3 of these 8 patients suffered from neurological deficits postoperatively. However, the mean arterial flow velocity of distal parent vessels in the group B increased by more than 30 percent in only 3 of the 15 patients and 2 of these 3 patients suffered from neurological deficits postoperatively. CONCLUSION: Isoflurane controlled hypotension may increase the incidence of cerebral vasospasm. Isoflurane induced hypotension for intracranial aneurysm surgery should be cautioned.

[The effect of intraoperative continuous nimodipine infusion on cerebral vasospasm during intracranial aneurysm surgery].

OBJECTIVE: To evaluate the effect of intraoperative continuous nimodipine infusion on cerebral vasospasm during intracranial aneurysm surgery. METHODS: Thirty consecutive patients under-going intracranial aneurysmal surgery were prospectively randomized into two groups: Isoflurane (group A, n = 15) and nimodipine (group B, n = 15). The patients in group A were maintained with 1 minimum alveolar concentration (MAC) isoflurane anesthesia during the whole procedure. The patients in group B were given nimodipine infusion continuously (20 microg.kg(-1).h(-1)) after induction of anesthesia and anesthetized with 1 MAC isoflurane. S100B levels in cerebrospinal fluid were determined before aneurysm clipping and 0, 2, 4 h after aneurysm clipping by enzyme linked immunosorbent assay. Assessment of mean blood flow velocity of parent arterial and arterial branches were performed before and after aneurysm clipping. RESULTS: (1) S100B in cerebrospinal fluid was increased significantly at 4 h after aneurysm was clipped in group A (F = 4.11, P < 0.05). However, S100B in cerebrospinal fluid was stable in group B in the whole procedure. (2) Mean arterial flow velocity of parent vessels in group B was lower significantly than that in group A (t = 2.08, P < 0.05). However, mean arterial flow velocity of distal vessels in both groups has no significant difference. CONCLUSION: Intraoperative nimodipine infusion may prevent cerebral vasospasm during intracranial aneurysm surgery.

Effects of desflurane on jugular bulb gases and pressure in neurosurgical patients.

The purpose of this study was to investigate the effect of different concentrations of desflurane on jugular bulb gases and jugular bulb pressure (JBP) and to determine an optimal concentration of desflurane in neurosurgical patients with supratentorial tumor. Twenty-two patients were anesthetized with desflurane in oxygen. Radial arterial and jugular bulb catheters were inserted for blood gas sampling and direct blood pressure measurement after anesthesia. Mean arterial blood pressure (MAP), heart rate (HR), and JBP were monitored continuously. Arterial and jugular bulb blood gases were measured at 0.7 minimum alveolar contraction (MAC) (4.2%), 1.0 MAC (6%), and 1.3 MAC (7.8%) of desflurane randomly after a 30-minute stabilization period, respectively. Jugular bulb oxygen saturation (S(J)O2) significantly increased and cerebral arteriojugular difference of oxygen content (A(J)DO2) and oxygen extraction ratio (O2ER) significantly decreased from 0.7 MAC to 1.0 MAC of desflurane, but there was no further increase in S(J)O2 nor further decreases in A(J)DO2 and O2ER at 1.3 MAC compared with 1.0 MAC desflurane. There was a significant dose-related decrease in MAP from 0.7 MAC to 1.3 MAC of desflurane, but JBP did not change significantly. No significant change in hour was observed in the study. It is concluded that 1.0 MAC is a suitable concentration of desflurane in neurosurgery with an improved balance between cerebral oxygen supply and demand.